Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net loss	$ (10,718)	$ (8,162)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation, amortization and write-off of property and equipment	688	604
Amortization and write-off of intangibles	639	520
Changes in allowance for doubtful accounts		16
Stock-based compensation	2,707	2,480
Changes in operating assets and liabilities:
Trade accounts receivable	2,139	1,509
Other current assets	52	36
Other assets	36	74
Accounts payable and other accrued liabilities	109	(160)
Deferred revenue	(917)	(1,285)
Net cash used in operating activities	(5,265)	(4,368)
Cash flows from investing activities:
Purchase of property and equipment	(755)	(324)
Capitalized patent costs	(436)	(428)
Maturity of marketable securities	22,467	15,363
Purchase of marketable securities	(8,819)	(12,412)
Net cash provided by investing activities	12,457	2,199
Cash flows from financing activities:
Exercise of stock options	309	1,129
Purchase of common stock	(1,104)	(1,035)
Net cash provided by (used in) financing activities	(795)	94
Net increase (decrease) in cash and cash equivalents	6,397	(2,075)
Cash and cash equivalents at beginning of period	3,160	6,122
Cash and cash equivalents at end of period	9,557	4,047
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net	14	2
Supplemental schedule of non-cash investing activities:
Property and equipment and patent costs in accounts payable	273	99
Stock-based compensation capitalized to software and patent costs	$ 75	$ 91